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It's always fun to talk about upgrading a fuel injection system. Typically, upgrading to a newer fuel injection system is better. Typically, upgrading to newer fuel injection system is more expensive. More often than not, gearhead-efi members upgrade fuel injection systems with a very limited budget.

Cost vs. Performance

OBD1 (1987 - 1995) is affordable and provides good performance.
OBD2 (1996 & newer) is less affordable, and usually performs better than OBD1.

The injector batch firing sequence for TPI is 1,3,5,7 and 2,4,6,8, ... that's a sun rise in the East and sun set in the West statement ... Meaning that is just the way it is.

MPFI - could mean Multi Point Fuel Injector, or could mean Multi Port Fuel Injection. When I see MPFI I think "One Injector Per Cylinder".

Years ago, Edelbrock offered a TBI to MPFI conversion fuel injection system. The system included a new intake manifold with 8 injectors "One Injector Per Engine Cylinder", custom chip, and a 8 injector pigtail to replace the TBI injector Connectors. It was a good system, that worked well for stock engines or engines modified with the "Edelbrock Camshaft Package". The Eledrock system did not "UPGRADE" the computer electronics for optimal injector firing. Link to the Edelbrock TBI to MPFI installation manual: https://static.summitracing.com/glob...multi-poin.pdf

The .pdf file posted above is a "How to OPTIMIZE" the 16168625 injector firing for MPFI - One Injector Per Cylinder.

Converting the 16168625 to MPFI has been very successful and a budget friendly upgrade for several gearhead-efi members.

the 7730 ecm only had one injector driver, so by batch fire they mean all 8 at a time. the 7749 had 2 drivers which is why they can be modified to do low impedance.

injector timing isn't all that important in a batch fire speed density setup with good quality small injectors. I think it means more when you're running big injectors with tiny open times at idle. that is where sequential injectors show good improvements in idle quality. but still not so much under load at higher rpm.

Sorry to buck, I knew of a Caddy that had such a set up of two on one bank and two on the other.

I did not see the wiring diagram before...interesting and informing.

So was what I read about the PCM in my 93 being a one year PCM correct?? If so is there a direct replacement that is better?

And can you commit on my ideas:

A few concerns in my case is all the major rewiring in my van, and as I understand things at this point, the OBDII Systems are very hard to get into to do tuning were the OBDI systems are basically wide open.

Also it seems much easily to enable the lean cruse system.

Lastly I want to tune for MPG and think a PCM with so called learning systems could fight and remove improvements in MPG to suit its core programing, where I think a OBDI system might be less able to reprogram fuel settings.

Also my Chip was already programed for a V8 350, in my van with its current drive train...once I make to changes to it and the PCM to run the TPI I believe it is all set to run my new engine.

Also where is the Lean Cruse function? In the Eprong or in the Main PCM?? I had a tuner years ago say he programed a Lean Cruse into my eprong, even sent a tail pipe sniffer to refine it.

Was that on the level?? It did not seem to make any changes and MPG did not change.

0411 sequential injection with coil per cylinder and a dual plane intake converted to EFI will make the most off-idle torque and give the best mileage. TPI is counter productive to torque in the RPM range you are looking to run. They are great for midrange in the 2,800-4,000 rpm range, not so good anywhere else.

I enable lean cruise all the time on 0411s.

The edelbrock TBI-MPFI intake would be great with an 0411 running it. Run the 0411 in speed density mode without the MAF. Then again your 4L60E would not play well with an 0411.

Well in Car Craft’s May 1989 issue in their article TPI Shown Down: they tested a 1998 Corvette L96 with its aluminum heads, stock but for Edelbrock’s 6873 IROC Tubular Exhaust system running through a stock 88 Cat for the testing. This made 253HP 4500RPMs and 328 lbs-ft at 3000 to 3500 RPMs.

The tested on Edelbrock’s Superflow 901 Dyno, which was able to pull numbers every 5 seconds and at each 500RPMs from 2000 to 5000.

So this base line engine did the following:

Torque:

RPMs torque
2000 296
2500 313
3000 328
3500 328
4000 316

That was only a gain of 32 Ft-Lbs from 2000 to 3000, the peek.

The stock specs for that car was:

Horsepower 245 net @ 4300 RPM
Torque 340 lb. – ft. @ 3200 RPM

My stock Van G20 350 made:

Power 188 hp @ 3800 rpm.
Torque 300.19 lb.-ft. @ 2400 rpm.

I will be running a 383, 193 swill port heads, and a roller cam rated for 2200 RPM torque peek, which I plan on advancing 4 degrees, which should shift the power curve to 2000RPMc.

To that I am adding a 383 and a tuned port system which is said to add 30% more Torque, HP and MPG to a stock engine.

So I should see 354 Ft-lb for a 350, how much more I will get with the 383 is not known but I bet it will be a little more. I found this: all other stuff left the same the difference between a 350 to a 383 a rough guesstimate is 35hp, 40 lb/ft torque.
So based on that I might see 394 ft-lb @ 2000 RPMs.

One as I will be using my vans stock OBDI TBI PCM modified to MPFI TPI: will the knock sensor work? I read somewhere a TPI knock sensor is different to a TBI version.

Two, as this system was a MAP system, where does the MAP sensor go?? I have hardly done anything with them.
It seems they are just mounted just about anywhere as it seems they do not need to be inside any part of the engine??

I wonder if the heat of under the hood can affect the pressure readings?

One as I will be using my vans stock OBDI TBI PCM modified to MPFI TPI: will the knock sensor work? I read somewhere a TPI knock sensor is different to a TBI version.

Two, as this system was a MAP system, where does the MAP sensor go?? I have hardly done anything with them.
It seems they are just mounted just about anywhere as it seems they do not need to be inside any part of the engine??

I wonder if the heat of under the hood can affect the pressure readings?

If you run the stock TBI computer the stock TBI knock sensor is the one to use.

MAP sensor bolts to a bracket that bolts to the passenger side rear of the TPI plenum. A short rubber elbow connects the MAP to the vacuum fitting on the plenum.

I had to mod the injector drivers by eliminating the current sense resistors and soldering a short piece of wire in place of each. After the chip was dialed in for the setup it ran really well. That being said I woke my old Vortec head TPI 383 out of its slumber, drove it around the country property and loaded it on a trailer with an otherwise stock TBI chip. Was a little rich on cold start but ran great even with the stock TBI programming. So I have faith that it will run on the stock TBI computer with hardware mods well enough for you to start the tuning process.

Now about the Injection system: "I had to mod the injector drivers by eliminating the current sense resistors and soldering a short piece of wire in place of each. After the chip was dialed in for the setup it ran really well."

What PCM were you using?? Can you tell me more on this??

And " Was a little rich on cold start" could that because of the 9th cold start injector?

I read somewhere of a system to cut in the 9th injector at WOT for MORE power...

Lastly "So I have faith that it will run on the stock TBI computer with hardware mods well enough for you to start the tuning process. " Good to know, and how much tuning was needed to get her dialed in?

How well did your 383 work out?

Thanks again for your help.

Rich

Originally Posted by Fast355

If you run the stock TBI computer the stock TBI knock sensor is the one to use.

MAP sensor bolts to a bracket that bolts to the passenger side rear of the TPI plenum. A short rubber elbow connects the MAP to the vacuum fitting on the plenum.

I had to mod the injector drivers by eliminating the current sense resistors and soldering a short piece of wire in place of each. After the chip was dialed in for the setup it ran really well. That being said I woke my old Vortec head TPI 383 out of its slumber, drove it around the country property and loaded it on a trailer with an otherwise stock TBI chip. Was a little rich on cold start but ran great even with the stock TBI programming. So I have faith that it will run on the stock TBI computer with hardware mods well enough for you to start the tuning process.

They now have roller lifters and I am very interested in using them in my engine.

The concept of making a cam into a broadband cam is a great idea, I would really like my engine to have a torque curve from 1500 to 3500RPM, giving it a great power as at 3500RPM HP should also be showing so it COULD run strong all the way to 4500/5000RPMs.

I am NOW looking into running a higher power cam and using Rhoads V-Max OE Roller lifters because they can give me my low RPM Torque and then allow the more power of a larger cam.

So if these are a good idea then I am looking for Chevy roller cam with these specs: (used would be good)

As close as possible to this: 184 to 206 intake duration 194 to 212 Exhaust duration, and 384 IT lift and 407 Ex lift.

I'm wondering how Rhoads Lifters will affect vacuum? If the vacuum signal is 100% consistent, then tuning will be predictable. The MAP sensor is used to control the fuel. If the vacuum signal going to the MAP is not consistent, then the fuel from the injectors will not be consistent either.

Rhoads lifters have been around a long time. I have followed them slightly, but because of a failure to advertise better had ruled them out for two reasons.

First they fail to show that they make roller lifters on their own web page, so I had not known anything about these roller lifters.

Second they were reported to make some noise, clicking, and were reported to cause problems with knock sensors. So they were said to not work well with FI engines.

Lastly they seem to be love them or hate them reaction.

Sense it was suggested I run them by a person on Third Gen Camaro as he claimed a flat torque power band from 2000 to 4000 in a fuel injected Camaro, and when I asked was told he was running the newer Rhoads V-Max OE Roller Variable Duration Lifters, I have looked up reports of users.

It seems pure power nuts prefer not to run them as the want ALL the HP they can get and feel it is not there all across their power band. Others LOVE them for their use.

As advertised most use them to tame hot cams. Which they were mainly invented to do. Variable Duration Lifters, or variable cams are becoming in much use in newer engines so these ideas are used more.

I am looking into them to broaden my own power band, I am looking into the idea of having a power band from 1500 to say 3000/3500 at which point I believe HP would take over all the way to the max of 5000.

I talked with Jack Rhoads himself (son of Mr. Rhords) about what I wanted to do and he suggested as they can shift a cam down by 20% I get a nearly stock cam one with say 20% more duration so that I would have my low RPM torque and with his lifters then have the full power of said cam at higher RPMS.

I was a little concerned with the torque power band of my engine, it being from 1800 to 2300, I was worried it would kind of fall on its face dropping power over 2300, so these seems to solve that problem.

The new Rhoads V-Max OE Roller Variable Duration Roller Lifters seems to have fixed the two main problems that had me ruling them out, they are making rollers and there are only a slight chance or problems with Fuel injections and clicking noise.

From Jpegs wed site:

“For maximum increases in low-end torque, engine vacuum and improved idle quality, our newly developed and newly patented Rhoads V-Max OE Roller Variable Duration Lifters are the answer. They increase low-end torque and engine vacuum up to 50% more than Orginal Rhoads Lifters...and they rev higher too. This makes them the best choice for hot street, performance marine and all racing applications. Typical vacuum increases range between 3 to 5 inches at idle when used with bigger cams. They are fully adjustable and require an adjustable valve train. Adjustment is similar to solid lifters. Simply use a feeler gauge to adjust the exact amount of lift reduction you want, anywhere from .010" to .030", and that is exactly what you get at idle. Duration is reduced between 5 and 20 degrees at .050" lift depending on the adjustment. As the rpm increases, so does the lift and duration. Full restoration takes place at approximately 4000 rpm. For engines equipped with adjustable valve trains, Rhoads V-Max OE Roller Lifters are definitely the best choice. They are particularly suited for racing applications with vacuum rules. You can run more cam than your competition while still meeting vacuum requirements, giving you the performance advantage. They are also useful in allowing larger cams to be used in computer controlled engines without disrupting proper computer functions.

Super Lube Groove

This option adds maximum lubrication and valve train longevity and is available with either Original or V-Max design lifters. A patented groove runs down the entire length of the lifter, constantly injecting oil on vital wear surfaces where lifter and cam face meet, eliminating the need for costly grooving modifications to the lifter bores in the engine block. Best of all, this addition does not in any way alter Rhoads lifter performance.